1. Field of the Invention
The present invention relates to a brake control apparatus, and more particularly to a brake control apparatus switching a control mode from an auto-braking mode, in which a brake force is controlled in accordance with a distance between a vehicle and a forward vehicle or obstacle, to a manual braking mode in which the brake force is controlled in accordance with a braking operation of a driver.
2. Description of the Related Art
Conventionally, a running control apparatus in which a distance between a vehicle and a forward vehicle is measured and a running control of the vehicle is performed, based on the measured distance and a speed of the vehicle, so that the distance between the vehicle and the forward vehicle is not less than a constant value has been proposed (Japanese Laid-Open Patent Application No.4-201692). In such a running control apparatus, a running state (the speed and/or acceleration) of the vehicle is controlled by the acceleration control and brake control (in an auto-braking mode) based on the measured distance between the vehicle and the forward vehicle and the speed of the vehicle. Then, for example, when a driver carries out a brake operation (an operation of stepping on a brake pedal) during the brake force control in the auto-braking mode, an intention of the driver takes priority over the brake force control in the auto-braking mode, so that the auto-braking mode is released. As a result, the vehicle is braked with a brake force depending on an amount of operation of the brake pedal (in the manual braking mode).
In the above mentioned conventional brake control apparatus, as shown in FIG. 1, when a brake force (a wheel cylinder pressure) Pw (=Pw1) is generated, the auto-braking mode may be switched to the manual braking mode. In this case, after the brake force Pw is rapidly decreased, the brake force Pw (=Pm: a master cylinder pressure) is gradually increased in accordance with the amount of braking operation (the amount of operation of stepping on the brake pedal). As a result, at a time ta at which the control mode is switched to the manual braking mode, the deceleration of the vehicle is temporarily decreased. At this time, the driver may feel a physical disorder, such as the vehicle advancing.